Electro-mechanical igniter



1962 D. J. ROBINSON ELECTRO-MECHANICAL IGNITER Filed June 24, 1960 Douglas J. Robinson,

INVENTOR \Nm Y mm 09 E ite 3,063,374 ELECTRO-MIECHANICAL IGNITER Douglas J. Robinson, Duarte, Calif., assignor to the United States of America as represented by the Secretary of the Army Filed June 24, 1960, Ser. No. 38,685 5 Claims. (Cl. 102-49) force for the firing pin and the solenoid was used for.

the release of the spring. In this type of mechanism, if a misfire should occur, it becomes necessary to disassemble the igniter mechanism to rearm it for another attempt at firing.

Also, a safety hazard exists in these conventional devices in that the spring could accidently be released thereby permitting the firing pin to detonate the cap and ignite the propellants.

, An object of this invention is to provide an igniter which can be repeatedly operated in case of misfires.

Another object is to provide an igniter wherein a greater margin of safety is achieved by the prevention of accidental or premature operation thereof.

The principal feature of the present invention is the utilization of a strong solenoid for directly driving a firing pin to contact and, therefore, detonate a primer cap located in a rocket motor chamber casing which encloses a combustible solid propellant disposed for combustion responsive to the detonation of the primer cap.

The firing device, enclosed within a housing, is secured to the combustion chamber and includes a solenoid iconnected to a source of electric energy. The solenoid has an armature or plunger slidably mounted therein and disposed for displacement along a rectilinear path responsive to the energization of the solenoid. Secured to the armature and carried therewith is a firing pin disposed to contact and detonate a primer cap which is located adjacent the solid propellant in the rocket motor combustion chamber and which, upon detonation, ignites the propellant. j,

Carried by'the firing pin is 'a resilient member to return the armature and firing pin back to their normal position responsive to their displacement. Therefore, if a misfire should occur it is merely necessary to re-energize the solenoid for another attempt at firing the rocket.

A safety feature of this invention is provided by the resilient member carried by the firing pin which also serves to hold the firing pin away from the cap until such time when detonation is desired.

Further aims and objects of the present invention will become more fully apparent from the following description and accompanying drawings in which:

The FIGURE is a sectional view of the firing device of this invention as used in connection with a rocket motor shown fragmentarily.

As shown in the drawing, a device for igniting the solid propellant of a rocket motor is provided by a firing assembly 12. The assembly 12 has a solenoid stator 14 made in the form of a spool with windings '16 around the spool and with one end of the windings abutting a stator body 20. The stator body 20 has an annular passage 22 cut axially therethrough. An armature 24, preferably made of mild steel, in the form of a cylindrical sleeve is disposed for slidable axial movement into and out of passage 22.

States Patent ()1 axial cavity 26 therethrough, and has an annular shoulder 27 protruding into the cavity 26 to define a restricted aperture 31 in the cavity 26.

To permit the attachment of a firing pin 28 to the armature 24, one end 29 of the firing pin 28 is externally threaded and extends through the aperture 31 to receive a nut 33 thereon.

The firing pin 28 extends from the armature 24 and through an aperture 32 in an end flange 18 of the assembly 12. The aperture 32 has an annular shoulder 34 therein to serve as a guide for the firing pin 28 and as a seat for one end of a spring 30 circumferentially mounted about the firing pin.

The spring 30 is disposed in the cavity 26 of armature 24 and is seated therein against shoulder 27. The spring 30 extends, with the firing pin, through the aperture 32 of flange 18 and is seated therein against shoulder 34 of flange 18.

Flange 18 is annularly recessed on its outer surface 36 to form a surface 40 and a shoulder 38 in stepped relation. An annular neck 42 extends in stepped relation from the inner surface 44 of flange 18 with an outside diameter matching the outside diameter of armature 24 and in coaxial alignment therewith.

To serve as a guide for armature 24 and for securing flange 18 and body 20 together, a tubular member 46 is disposed on the outer surface 48 of the neck 42 and extends therefrom to surround and be secured to the outer surface 50 of armature 24 and to bear against a shoulder formed by an annularly cut back portion 52 of the passage 22 of stator body 20. I

To provide a mount for an outer cylindrical casing-54, the stator body 20 has an outside diameter matching the diameter of the annular recess of flange 18. The casing 54 fits onto the recessed surface 40 of flange 18'an'd surrounds the stator body 20. An end plate 56 is secured to body 20 by any suitable means to hold the casing 54 in place between the end plate and flange'18'.

In order to effect a seal between end plate 56 and stator body 20 an annular groove 58'is provided in the outer surface 60 of stator body 20 to'receive therein a seal 61 which may be any of the conventional O-ring types.

The cylindrical casing 54 has a sleeve 64 rotatably mounted thereon and extending from an inner. end 66 of the sleeve to a'point intermediatethe ends of the casing. The sleeve 64 is externally screw-threaded at it inner end 66 and so mounted that the inner end 66 abuts against shoulder 38 of flange 18.

To hold sleeve 64 in place the cylindrical casing 54 is provided with an annular groove 70 adapted to receive therein a snap ring 72 which fits snugly against the outward end 74 of sleeve 64 thereby retaining sleeve 64 in place.

To permit a source of electrical energy to reach coils 16 of stator 14 there is provided a longitudinal bore 76 through end plate 56 and through stator body 20 which can receive therethrough electrical leads 78 connected from an external source of electrical energy (not shown).

To attach the firing assembly 12 to casing 81 of a combustion chamber of a rocket motor 82 there is provided in the top 83 of the rocket motor a booster block 84 which has a large annular cavity 86 therein. The cavity 86 is internally screw threaded to match the external screw threading of the inner end 66 of sleeve 64 thereby permitting the ignition device 12 to be secured onto motor 82.

The booster block 84 has an axial bore 88 therethrough which communicates with the cavity 86 and which is adapted to receive a collar 90 therein. The inner end 92 of the collar 90 abuts against the outer surface 93 of flange 18. There is provided at the inner end 92 of collar 90 an annular groove adapted to receive a sealing ring 94 3 between flange 18 and collar 90. The outer end 95 of collar 90 is internally screw threaded to receive therein an externally screw threaded primer cap 96. The cap 96 is located in the collar 90 adjacent the combustion chamber 80 of the rocket motor.

To enable the assembly 12 to be unlatched and swung open there is provided between the booster block 84 and assembly 12 a pivotal retaining means 98. The retaining means 98 comprises a narrow, heavy, metal slip ring 100 rotatably mounted on sleeve 64 and having a pivot eye 102 radially mounted thereon. The eye 102 is secured to booster block 84 as by welding. Two handles 104 are mounted on opposite sides of the sleeve 64 to permit sleeve 64 to be unscrewed from the booster block 84 for opening of the assembly 12.

Responsive to the unscrewing of sleeve 64 from the booster block 84 the retaining means 98 and the firing device 12 swings in an arcuate path about the pivot eye 102 to permit access to the interior of firing device 12 while also holding firing device 12 in its open position on booster block 84.

As electric energy is supplied through connections 76 to the coils 16 of stator 14 a magnetic field is induced in these coils which expels armature 24 and firing pin 28 from the passage 22 of stator 14 in a rectilinear path causing the firing pin 28 to contact primer cap 96 causing it' to detonate and ignite the propellant in the combustion chamber 80 of rocket motor 82.

Due to the movement of the firing pin 28 as described above the spring 30 carried by firing pin is forced from a normal to a compressed state. After the firing pin strikes the primer cap 96 it, along with the armature, is returned to the normal position by virtue of spiral 30 expanding from its compressed state back to its normal position. This above described movement permits repeated operation of the igniter should a misfire occur.

I claim:

1. In a rocket motor of the type having a motor chamber, a combustible solid propellant and a primer cap for igniting the propellant disposed in said chamber, a firing assembly including a housing, means for attaching said firing assembly to said rocket motor comprising a booster block having a large internally screw threaded annular cavity therein and a longitudinal bore in axial alignment and communicating with said cavity, a collar disposed within said bore having a portion extending into said chamber, a primer cap disposed in said extended portion, a sleeve rotatably carried by said housing and externally screw threaded to match the internal screw threading of said cavity to provide for the attachment of said firing assembly and said combustion chamber, a slip ring rotatably 4 W F mounted on said sleeve, a pivot eye radially mounted on said slip ring and secured to said booster block to permit said housing to swing open in an arcuate path about said pivot eye responsive to the unscrewing of said sleeve from said booster block for the opening of said housing.

2. The device as set forth in claim 1 wherein the firing assembly comprises: a solenoid mounted in said housing, said solenoid provided with a stator having coils wound thereon; an armature slidably disposed in said stator; a firing pin secured to said armature for slidable movement therewith; a source of electrical energy connected to said coils for energization thereof, said armature disposed for displacement of said firing pin from a normal position to impact with said primer cap for detonation of said rimer cap responsive to energization of said coils.

3. The device as set forth in claim 2 further comprising: an end flange secured within said cavity of said booster block and provided with an axial aperture therethrough and an annular shoulder protruding into said aperture, said armature provided with an axial cavity therethrough and an annular shoulder protruding into said cavity of said armature, said firing pin secured within said cavity of said armature and extending therefrom through said aperture of said end flange to be guided in its slidable movement by said shoulder of said end flange; a spring circumferentially mounted about said firing pin and seated at one end against said shoulder of said armature and extending therefrom into said aperture of said end flange to be seated at its other end against said shoulder of said end flange, said spring disposed for return of said firing pin to said normal position responsive to said slidable movement.

4. The device of claim 3 wherein said housing includes an end plate secured to said stator; a tubular member secured between said stator and said end flange to serve as a guide for said armature in its slidable movement; said housing having an outwardly disposed annular groove thereon and disposed within said sleeve; a snap ring disposed in said groove of said housing and in engagement with the end of said sleeve for retention thereof on said housing.

5. The device of claim 4 wherein said end plate and said stator are provided therethrough with aligned longitudinal bores; electrical conductors disposed in said bores and connected to said source of electrical energy and to said coils for energization thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

